Police have said there was no sign of the car when they examined the scene soon after the landslip happened and explained they were under huge pressure to deal with hundreds of incidents caused by the bad weather.

But the Independent Police Complaints Commission said on Wednesday that the force was sending details of the tragedy to it for it to consider.

The IPCC said: "Dorset police will be referring the Beaminster tunnel landslip deaths. This will be assessed and a decision made about the mode of investigation."

It emerged that the couple had cut short a restaurant meal and were hurrying home because they were concerned about the torrential rain.

Neither has been formally identified by police but they have been named locally as Rosemary Snell, 67, who had recently moved from London, and retired surgeon Michael Rolfe, 72.

On the evening of the landslip on 7 July, the couple, both from Somerset, were dining at the Bridge House Hotel in Beaminster. The pair used to visit the hotel three or four times a year and had celebrated Valentine's Day there.

Jane Fox, who served the couple, said: "It was a very atrocious night. She was concerned about the weather. She said, 'We'll skip coffee because we really want to get off.'

"That was about 10.05pm and we think the landslide occurred at about 10.10pm – so it was a matter of a few minutes. If they had the coffee they would still be here.

"They were delightful, especially her – she was very effervescent and outgoing, a true lady. It has been a great shock for all of us. They were a genuinely nice couple, who were always very chatty and interested in each other.

"She always appeared immaculately dressed, they were simply a pleasure to serve and have as our guests."

Fox said shortly after the couple left the restaurant, kitchen and reception staff left work but by that time the landslip had occurred and they were forced to turn back on the road, unaware that Snell and Rolfe had been caught in the mud and rubble.

Louise Brister, who cleaned Rolfe's house, said: "He was such a nice, caring guy. He was always laughing, so bright and cheerful, and had only recently met Rosemary Snell. He loved his bridge and was keen on cricket. I'm in shock and can't believe it."

Police became concerned for the couple when Rolfe's family raised the alarm. Detectives used phone and bank card records to narrow their movements down to the area around the landslip. Emergency workers found the mud-filled car on Monday evening.

Nobody from Dorset police was available to comment on the referral to the IPCC.